1. Field of the Invention
The present invention relates to a die bonder, and particularly to a method of removing foreign substances of a collet that picks up a die from a wafer.
2. Description of the Related Art
The die bonder is an apparatus that bonds (mounts and bonds) dies (chips of silicon substrates on which electric circuits are formed) to a lead frame or a substrate (hereinafter, referred to as a substrate) using solder, gold plating or resin as bonding material. It should be noted that an apparatus that actually performs bonding is provided in the subsequent process as an adhesive agent or the like is hardened depending on the type of the die bonder. Thus, “bonding” principally means “mounting” in the specification.
In a die bonding apparatus (die bonder) that mounts (bonds) a semiconductor chip called “die” on the surface of a substrate such as a printed circuit board or a lead frame, an operation (work) in which the semiconductor chip is carried onto the substrate using an absorption nozzle called “collet” to apply a pressing force, and bonding material is heated to perform bonding is repeated in general.
The collet is a retainer that has a hole in the middle and absorbs a die by sucking the air.
Using FIG. 9, an operation of a conventional die bonder will be described while focusing on a pickup operation in which dies are picked up from a wafer. FIG. 9 is a flowchart for explaining an embodiment of a procedure of a collet cleaning operation by a conventional die bonder. This operation is controlled in such a manner that a control unit of the die bonder mutually accesses the respective devices of the die bonder.
In a wafer setting step S11, a wafer configured using dies used for die bonding is set (supplied) to a pickup device.
Next, in an initial value setting step S12, the die bonder is initialized, map data for dies of the set wafer is written, and an implementation program for die bonding (mounting) of the dies on a desired substrate is written.
Next, in a die starting position reading step S13, a position (starting position) from which the dies are started to be picked up is read from the map data written in the initial value setting step S12.
Next, in a die bonding step S14, the dies are picked up from the starting position read in the step S13 to execute the die bonding.
Ina die presence/absence confirmation step S15, it is confirmed whether or not the dies are present in the set wafer. If the dies are present, the flow is moved to the process of a die bonding completion confirmation step S16. If not, the flow is moved to the process of the wafer setting step S11.
In the die bonding completion confirmation step S16, it is confirmed whether or not the die bonding has been executed for the all substrates. In the case where the die bonding has not been executed for the all substrates, the flow is moved to the process of the die bonding step S14. In the case where the die bonding has been executed for the all substrates, the die bonding is completed.
In the case of using such a collet, it is necessary for the collet to absorb the die. Thus, in the case where foreign substances such as metal, resin, or dust generated in, for example, a dicing process are attached into a gap between the die and the tip end (absorption surface) of the collet, there is a possibility that elements or protective films of the dies are damaged, or wirings are disconnected.
Therefore, an operator regularly and frequently dismounts the collet from the apparatus for replacement or cleaning. Thus, it is necessary to stop the die bonder every time the collet is cleaned, leading to reduction in the operating rate of the apparatus.
Accordingly, for example, Japanese Patent Application Laid-Open No. H6-302630 describes an apparatus in which a die is absorbed at the tip end of a collet to be mounted on a lead frame. During the process, when foreign substances attached to the tip end of the collet are removed for die bonding, the tip end of the collet is imaged by a camera such as an ITV to determine the presence of absence of foreign substances. As a result, the collet is heated or cleaned, and then the air is blown to remove the foreign substances.
There has been used a method from the past in which the foreign substances are blown off by air blowing as described in, for example, Japanese Patent Application Laid-Open No. H6-302630, or the foreign substances are removed by a metal brush. Therefore, it has been necessary to add a unit such as an air blowing mechanism or a brushing mechanism.
Further, it has been impossible to remove the foreign substances with high adhesive power by air blowing or brushing.
Further, even if the foreign substances can be removed, there has been a risk that the removed foreign substances scatter to be attached to the product.
In view of the above-described problems, an object of the present invention is to provide a collet cleaning method and a die bonder using the same in which a collet can be cleaned without adding a new unit, and foreign substances with high adhesive power can be reliably removed without scattering the foreign substances.